[defrost]

As I understand it "dusting crops" is commercial aerial work and thus outside of

  General aviation (GA) is defined by the International Civil Aviation Organization (ICAO) as all civil aviation aircraft operations except for commercial air transport or aerial work, which is defined as specialized aviation services for other purposes

~ https://en.wikipedia.org/wiki/General_aviation

Crop dusting, small frame fire suppression, and small frame geophysical surveying are often single pilot- and geophys surveys can drape entire countries at 80m ground clearance and 200m line spacing (plus transverse lines) so they can really rack up the hours and line kilometres.